This category D study, sponsored by Bristol Meyer-Squibb, has been completed. Endothelins represent a family of vasoactive peptides which have a prominent role in the regulation of vascular tone and blood pressure. Endothelins also play a role in conditions associated with chronic vasoconstriction, such as congestive heart failure. Receptors for endothelins exist on smooth muscle cells of vascular walls, and the drug under study, BMS-193884, is a selective antagonist for one of the key endothelin receptors. A safe therapeutic dose range was defined in this study, and the drug also proved efficacious in treating heart failure. Data collected has been forwarded to the drug company sponsor for final analysis and publication.